Pneumatic fastener driving device

ABSTRACT

A pneumatic fastener driving device wherein a cylinder houses a piston that is adapted to be driven therethrough by air pressure. A driving blade connected to the piston extends through the cylinder and strikes a fastener, e.g., a nail. A buffer in the bottom of the cylinder cushions the impact of the piston upon reaching the end of its stroke. A chamber surrounding the cylinder is supplied with air pressure during the downward stroke of the piston which is released at the end of the stroke against the bottom side of the piston to return it to its starting position. An air deflecting collar protects the buffer by deflecting air from the chamber away from the buffer and against the bottom of the cylinder.

United States Patent [1 1 Pomeroy Dec. 4, 1973 PNEUMATIC FASTENER DRIVING DEVICE [75] Inventor: Raymond Visher Pomeroy, Portland,

Oreg.

[73] Assignee: Omark Industries, Inc., Portland,

Oreg.

[22] Filed: Aug. .24, 1972 21 Appl. No.: 283,517

2/ 1970 Wandel et a1 227/130 X 8/1970 Perkins 227/130 X Primary Examiner-Granville Y. Custer, Jr. Attorney-Robert L. Harrington [57] ABSTRACT A pneumatic fastener driving device wherein a cylinder houses a piston that is adapted to be driven therethrough by air pressure. A driving blade connected to the piston extends through the cylinder and strikes a fastener, e.g., a nail. A buffer in the bottom of the cylinder cushions the impact of the piston upon reaching the end of its stroke. A chamber surrounding the cylinder is supplied with air pressure during the downward stroke of the piston which is released at the end of the stroke against the bottom side of the piston to return it to its starting position. An air deflecting collar protects the buffer by deflecting air from the chamber away from the buffer and against the bottom of the cylinder.

2 Claims, 2 Drawing Figures PNEUMATIC FASTENER DRIVING DEVICE HISTORY This invention relates to a pneumatic fastener driving device and more particularly to an improvement for increasing the performance of the device (also referred to herein as a pneumatic nailer).

As common for large building projects in the construction industry, the speed by which the many thousands of nails can be driven by an pneumatic nailer is an advantage that is highly desired over the manual methods used in the past. Thus, it will be understood that it is important that the pneumatic nailers be relatively trouble free and long lasting under adverse con-- ditions in order to maintain this speed advantage. In a pneumatic or air operated nailer there is relatively few moving parts which can cause breakdown. Primarily such devices include trigger operated valves for introducing air into a cylinder which then drives a piston through the cylinder and against the fastener. Additionally provided is a means for returning the piston to its starting position.

In one type of pneumatic nailer, the means for returning the piston includes a chamber provided around the cylinder in which air pressure is forced upon the down stroke of the piston.- When the pressure over the piston is released, the compressed air in the chamber is directed at the bottom of the piston and returns it to its initial position. It will be understood that it is desirable to provide a cushion at the end of the piston stroke to absorb the shock of the piston reaching the limit of its stroke. Cushioning devices commonly used are constructed so as to compress or flex upon impact of the piston and are subject to rapid wearing. The cushioning device is thus a vital factor in determining trouble free operational time of the pneumatic nailer. This wearing has been found to be greatly accelerated by reason of the introduction of the air from the outer chamber, which in previous designs has been directed against the buffer. This impingement of high pressure air has caused grooving and deterioration of the buffer, decreasing the life of the buffer and necessitating frequent changes.

BRIEF DESCRIPTION The present invention is believed to greatly increase the life of pneumatic nailers as generally described above by greatly increasing the life of the described buffer. Very briefly, this is accomplished by arranging the air inlets between the outer chamber and the cylinder so that the air jets are directed against a metal ring which'is provided around the base of the buffer. This ring is designed to deflect the air upwardly against the bottom of the piston. Such deflection increases performance by more efficiently utilizing the force of the air, (in prior devices some of the available energy produced by the air jets was absorbed by the buffer) and more importantly it guards the buffer against the direct impact of the air. It has been found that the buffer life is increased by as much as 300 to 500 percent by reason of this improvement.

Having thus only briefly described the invention, it will be more clearly understood by reference to the following detailed description and drawings wherein:

FIG. 1 is a view of a pneumatic fastening device incorporating the present invention; and

FIG. 2 is an enlarged view of a segment of the pneumatic nailer of FIG. 1 but more clearly showing the improvement comprising the present invention.

Referring to FIG. 1 of the drawings, the illustrated pneumatic nailer is comprised of a handpiece 10, a head assembly 12, trigger mechanism 14, magazine 16, and nose piece 18. The nose piece 18 is of common construction and adapted to receive fasteners, e.g., nails, in a manner known to the industry. The magazine 16 is also of a construction known to the industry and is adapted to receive nails provided in collated form with means to automatically feed the nails sequentially to the nose piece 18. The handpiece 10 encloses chamber 20 which receives air pressure from an inlet 22 connected to an air pressure supply line (not shown). The trigger mechanism 14 includes an air valve 24 that defines an inner chamber 25. Air pressure from the air chamber 20 is passed into inner chamber 25 through a portal 26. A piston 28 (with sealing ring 30) is slideable in inner chamber 25 between a first position as shown permitting the air pressure in chamber 20 to pass through the air valve and into the air passage 32, and a second position where portal 26 is sealed and the air passage 32 is opened to atmospheric pressure.

Trigger mechanism 14 includes a trigger 34 which is pivoted at pivot point 36. A toggle 38 is pivotally connected to the bottom of piston 28 at pivot point 40. As will be noted from the dotted lines showing the trigger 34 pivoted by the operator to its release position, the toggle 38 is tipped back. (It will be obvious that such trigger movement by itself will not raise the piston 28.) A probe 42 is adapted to slidingly engage the front end of the toggle 38. This probe is carried by guides and extends below the noise piece 18 as indicated by the projecting portion 44. This projecting portion 44 is adapted to engage the work surface, thereby raising the probe against the front end of the toggle 38. (It will also be obvious that without the trigger movement described above, the toggle will merely rock forward without moving the piston 28.) Combining the operations of moving the trigger to its release position and forcing the nose piece against a work surface will cause both ends of the toggle to be raised thereby forcing upper movement of the piston and closing of the air passage 26.

The head assembly 12 is comprised of a cylinder 46 which defines a chamber 48. A piston 50 is adapted to slide in the chamber 48 and by reason of sealingring 52 carried by the piston functions to seal off that portion of the chamber 48 above the piston from the portion of the chamber 48 below the piston. A driving blade 54 is secured to the piston and extends through the bottom of the cylinder into the nose piece 18. It willbe understood that this driving blade 54 is adapted to engage a fastener which is positioned in the nose piece. Positioned above the piston in the cylinder is a control valve 56. The control valve includes a sealing flange 58 which controls communication of the portion of the chamber 48 above the piston 50 with a passageway 60 which opens to the atmosphere, i.e., with the sealing flange in a lower position as shown the passageway 60 is opened to the chamber 48. A chamber 62 within the head assembly and surrounding the control valve 56 is connected through a passageway (not shown) to the air passage 32 in the trigger mechanism 14. With the portal 26 open, air pressure passes into chamber 62 and acting against the lower rim 63 carried by the sealing flange 58, holds the sealing flange 58 in the lower position (chamber 48 thus opened to atmospheric pressure). It will be noted that with the sealing flange 58 in its lower position, a seal 65 on the bottom of the rim 63 seats on the top edge of the cylinder 46 to close off communication of air pressure from chamber 20 to the chamber 48. It will be understood that by removing the air pressure from chamber 62 air pressure in chamber 20 acting against the shoulder 66 of the rim 63 raises the sealing flange 58 to thereby close off passageway 60. Such raising of the flange 58 also opens the chamber 48 to the air pressure in chamber 20.

Referring again to the trigger mechanism, the portal 32 is communicated through a passageway to chamber 62. Thus, by reason of air pressure from chamber 20 present in chamber 62, the sealing flange 58 is held in its lower position allowing atmospheric pressure to be present on top of the piston. Actuating the trigger mechanism, i.e., by raising the probe 42 and pulling the trigger 34, the piston 28 ismoved upward in the air valve 24 to close off portal 26 and open portal 32 to the atmosphere. This releases the air pressure from chamber 62 thereby allowing the raising of the sealing flange 58 which then closes off passageway 60 and opens the chamber 48 to the air pressure of chamber 20. This pressure drives the piston downward in the cylinder.

The force of the piston being driven downward which remains after driving a fastener is absorbed by a buffer 70. This driving downward of the piston forces air contained in the lower part of the cylinder through openings 72 located around the lower end of the cylinder and into a chamber 74. Upon reaching its lower most position, the piston passes below openings 76 and air pressure from above the cylinder also passes into the chamber 74. As the trigger mechanism is released, it will be understood that air pressure is once again built up into chamber 64 and with the assistance of return spring 64 returns the sealing flange 58 to its lower position. Passageway 60 is opened and the air pressure above the piston is released to the atmosphere. Thus, the air pressure in chamber 74 passing through the openings 72 forces raising of the piston.

In the present improved pneumatic fastener driving device, the buffer 70 is designed to accommodate a metal ring 80 which surrounds the lower part of the buffer in line with the air jets created by air passing from chamber 74 through openings 72. In that the metal ring is of rigid construction, it effectively and efficiently deflects the air jets upwardly against the bottom surface of the piston to raise it to its starting position in the cylinder.

Whereas pneumatic fastener driving devices contemwill recognize the value of the improvement provided herein and in becoming aware of the improvement, contemplate variations, revisions and modifications of that improvement, it is to be understood that the invention contemplates such variations, revisions and modifications. Thus, the invention and its protection are not to be limited to the described embodiment but to the claims appended hereto. Eaving thus described my invention,

what I claim is:

l. A pneumatic fastener driving device comprising: a head assembly, a cylindrical chamber in said head assembly, a piston movable in the cylindrical chamber from a starting position at one end of the chamber toward the other end, a driving blade fastened to one side of the piston for extending toward and through said other end of the cylindrical chamber with movement of the piston, fastener feeding means for feeding fasteners into the path of the driving blade to be driven by the driving blade into a work surface, means for supplying air pressure to said cylindrical chamber on the side of the piston opposite the driving blade when said piston is in its starting position, an air control valve controlling air pressure from the air pressure supply means into the cylindrical chamber, a chamber within the head assembly surrounding the cylindrical chamber, a shock absorbing buffer in the cylindrical chamber at said other end to limit the stroke of the piston and to absorb the impact of the piston upon reaching that limit, openings between the surrounding chamber and the cylindrical chamber adjacent the buffer whereby driving of the piston forces air into the surrounding chamber creating therein a positive pressure, means for evacuating the air pressure from the air pressure inlet side of the piston whereby air pressure in the surrounding chamber is directed back through the openings to return the piston to its starting position, and the improvement which comprises a rigid protective shield between the buffer and the openings to deflect the air from the buffer and toward the piston.

2. A pneumatic fastener driving device as defined in claim 1 wherein thebufier is elastomeric and frustoconical in form, and the protective shield is a metal rigid ring surrounding the base of the frusto-conical bufi'er. 

1. A pneumatic fastener driving device comprising: a head assembly, a cylindrical chamber in said head assembly, a piston movable in the cylindrical chamber from a starting position at one end of the chamber toward the other end, a driving blade fastened to one side of the piston for extending toward and through said other end of the cylindrical chamber with movement of the piston, fastener feeding means for feeding fasteners into the path of the driving blade to be driven by the Driving blade into a work surface, means for supplying air pressure to said cylindrical chamber on the side of the piston opposite the driving blade when said piston is in its starting position, an air control valve controlling air pressure from the air pressure supply means into the cylindrical chamber, a chamber within the head assembly surrounding the cylindrical chamber, a shock absorbing buffer in the cylindrical chamber at said other end to limit the stroke of the piston and to absorb the impact of the piston upon reaching that limit, openings between the surrounding chamber and the cylindrical chamber adjacent the buffer whereby driving of the piston forces air into the surrounding chamber creating therein a positive pressure, means for evacuating the air pressure from the air pressure inlet side of the piston whereby air pressure in the surrounding chamber is directed back through the openings to return the piston to its starting position, and the improvement which comprises a rigid protective shield between the buffer and the openings to deflect the air from the buffer and toward the piston.
 2. A pneumatic fastener driving device as defined in claim 1 wherein the buffer is elastomeric and frusto-conical in form, and the protective shield is a metal rigid ring surrounding the base of the frusto-conical buffer. 